Update lldb to track recent Triple arm64 enum removal and collapse into aarch64.

See the following llvm change for details:

r213743 | tnorthover | 2014-07-23 05:32:47 -0700 (Wed, 23 Jul 2014) | 9 lines
AArch64: remove arm64 triple enumerator.

This change fixes build breaks on Linux and MacOSX lldb.